Filter elements can be used to remove contamination in a variety of applications. Such elements can include a web of fibers. The fiber web provides a porous structure that permits fluid (e.g., gas, liquid) to flow through the element. Contaminant particles contained within the fluid may be trapped on the fiber web. Depending on the application, the fiber web may be designed to have different performance characteristics.
Fiber webs can be manufactured using conventional equipment. During manufacturing, fibers may be laid down in a continuous process to produce the web. This can lead to fiber alignment and the fiber web having a “machine direction” which is defined by the direction in which the web moves along the processing equipment, and a “cross-machine direction” which is perpendicular to the machine direction. Because of the fiber alignment, amongst other effects, properties of the fiber web along the machine direction can differ from properties along the cross-machine direction.
It may be advantageous to increase the effective surface area of the fiber web in some applications. For example, the fiber web may be waved to increase surface area. Such waves are generally referred to as corrugation, if they extend in the machine direction of the fiber web. The waves are called “flutes” if they extend in the cross-machine direction. The waved fiber webs can be combined with a backing layer to form channels through which fluid may flow. Some filter element configurations can take advantage of the channels and increased surface area provided by using fluted webs or by using corrugated webs. The machine direction and cross-machine direction properties of the web can play a role in its suitability for use in a particular configuration.
For various applications, it may be beneficial to have filter media with increased dust holding capacity. In addition, for some applications, filter media may be manufactured to have low thickness. However, in manufacturing filter media, when maintaining pore size and efficiency, a trade off may exist between having a high dust capacity and a low thickness of the filter media.